1,117 research outputs found
Mutually Unbiased Bases and Trinary Operator Sets for N Qutrits
A complete orthonormal basis of N-qutrit unitary operators drawn from the
Pauli Group consists of the identity and 9^N-1 traceless operators. The
traceless ones partition into 3^N+1 maximally commuting subsets (MCS's) of
3^N-1 operators each, whose joint eigenbases are mutually unbiased. We prove
that Pauli factor groups of order 3^N are isomorphic to all MCS's, and show how
this result applies in specific cases. For two qutrits, the 80 traceless
operators partition into 10 MCS's. We prove that 4 of the corresponding basis
sets must be separable, while 6 must be totally entangled (and Bell-like). For
three qutrits, 728 operators partition into 28 MCS's with less rigid structure
allowing for the coexistence of separable, partially-entangled, and totally
entangled (GHZ-like) bases. However, a minimum of 16 GHZ-like bases must occur.
Every basis state is described by an N-digit trinary number consisting of the
eigenvalues of N observables constructed from the corresponding MCS.Comment: LaTeX, 10 pages, 2 references adde
Characterization of Binary Constraint System Games
We consider a class of nonlocal games that are related to binary constraint
systems (BCSs) in a manner similar to the games implicit in the work of Mermin
[N.D. Mermin, "Simple unified form for the major no-hidden-variables theorems,"
Phys. Rev. Lett., 65(27):3373-3376, 1990], but generalized to n binary
variables and m constraints. We show that, whenever there is a perfect
entangled protocol for such a game, there exists a set of binary observables
with commutations and products similar to those exhibited by Mermin. We also
show how to derive upper bounds strictly below 1 for the the maximum entangled
success probability of some BCS games. These results are partial progress
towards a larger project to determine the computational complexity of deciding
whether a given instance of a BCS game admits a perfect entangled strategy or
not.Comment: Revised version corrects an error in the previous version of the
proof of Theorem 1 that arises in the case of POVM measurement
Structural Relaxation and Frequency Dependent Specific Heat in a Supercooled Liquid
We have studied the relation between the structural relaxation and the
frequency dependent thermal response or the specific heat, , in a
supercooled liquid.
The Mode Coupling Theory (MCT) results are used to obtain
corresponding to different wavevectors. Due to the two-step
relaxation process present in the MCT, an extra peak, in addition to the low
frequency peak, is predicted in specific heat at high frequency.Comment: 14 pages, 13 Figure
Bogomol'nyi equations for solitons in Maxwell-Chern-Simons gauge theories with the magnetic moment interaction term
Without assuming rotational invariance, we derive Bogomol'nyi equations for
the solitons in the abelian Chern-Simons gauge theories with the anomalous
magnetic moment interaction. We also evaluate the number of zero modes around a
static soliton configuration.Comment: 9 pages, Revtex, SNUTP-94/6
Quantum Entanglement dependence on bifurcations and scars in non autonomous systems. The case of Quantum Kicked Top
Properties related to entanglement in quantum systems, are known to be
associated with distinct properties of the corresponding classical systems, as
for example stability, integrability and chaos. This means that the detailed
topology, both local and global, of the classical phase space may reveal, or
influence, the entangling power of the quantum system. As it has been shown in
the literature, the bifurcation points, in autonomous dynamical systems, play a
crucial role for the onset of entanglement. Similarly, the existence of scars
among the quantum states seems to be a factor in the dynamics of entanglement.
Here we study these issues for a non-autonomous system, the Quantum Kicked Top,
as a collective model of a multi-qubit system. Using the bifurcation diagram of
the corresponding classical limit (the Classical Kicked Top), we analyzed the
pair-wise and the bi-partite entanglement of the qubits and their relation to
scars, as a function of the critical parameter of the system. We found that the
pair-wise entanglement and pair-wise negativity show a strong maximum precisely
at the bifurcation points, while the bi-partite entanglement changes slope at
these points. We have also investigated the connection between entanglement and
the fixed points on the branch of the bifurcation diagram between the two first
bifurcation points and we found that the entanglement measures take their
extreme values precisely on these points. We conjecture that our results on
this behaviour of entanglement is generic for many quantum systems with a
non-linear classical analogue.Comment: 14 pages, 6 figures in separate ps files, submitted for publicatio
Degree of entanglement for two qubits
In this paper, we present a measure to quantify the degree of entanglement
for two qubits in a pure state.Comment: 5 page
Tomography of fast-ion velocity-space distributions from synthetic CTS and FIDA measurements
We compute tomographies of 2D fast-ion velocity distribution functions from synthetic collective Thomson scattering (CTS) and fast-ion D-alpha (FIDA) 1D measurements using a new reconstruction prescription. Contradicting conventional wisdom we demonstrate that one single 1D CTS or FIDA view suffices to compute accurate tomographies of arbitrary 2D functions under idealized conditions. Under simulated experimental conditions, single-view tomographies do not resemble the original fast-ion velocity distribution functions but nevertheless show their coarsest features. For CTS or FIDA systems with many simultaneous views on the same measurement volume, the resemblance improves with the number of available views, even if the resolution in each view is varied inversely proportional to the number of views, so that the total number of measurements in all views is the same. With a realistic four-view system, tomographies of a beam ion velocity distribution function at ASDEX Upgrade reproduce the general shape of the function and the location of the maxima at full and half injection energy of the beam ions. By applying our method to real many-view CTS or FIDA measurements, one could determine tomographies of 2D fast-ion velocity distribution functions experimentally
Hydrography, bacteria and protist communities across the continental shelf and shelf slope of the Andaman Sea (NE Indian Ocean)
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